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SOLID WASTE LEACHING CHEMISTRY AND TESTING: A COMPREHENSIVE APPROACH TO ASSESS FUNDAMENTAL PARAMETERS (PRESENTATION)
Citation:
AL-ABED, S. R. AND G. JEGADEESAN. SOLID WASTE LEACHING CHEMISTRY AND TESTING: A COMPREHENSIVE APPROACH TO ASSESS FUNDAMENTAL PARAMETERS (PRESENTATION). Presented at International Conference on Energy, Environment and Disasters (INCEED 05), Charlotte, NC, July 24 - 30, 2005.
Impact/Purpose:
to present information
Description:
Worldwide, various anthropogenic activities generate hazardous solid wastes that are affluent in heavy metals, which can cause signficant damage to the environment and human health. The toxicity and the bioavailability of these metal contaminants depend on their reactivity and solubility, which in turn are determined by their speciation. Heavy metals such as Cu, Zn and Pb oxianion such as As, Se and Mo can exist in multiple oxidation states, and can undergo oxidation or reduction when they interact with mineral surfaces or organic compounds. One of the major problems with solid wastes is the generation of large quantities of heavily contaminated leachate, which can cause extensive pollution of ground and surface aquatic bodies. In the U.S., the Environmental Protection Agency (EPA) Toxicity Characteristic Leaching Procedure (TCLP) is one of the most common tests used by regulatory agencies for classifying and comparing the leaching characteristics of different waste matrices. The test involves mixing a crushed waste sampled in a buffered acetic acid solution of 18 h at 30 rpm, and analyzing the leachate. However, the test has several practical limitations and hence it is not applicable to the real waste systems. Most solid wastes are solidified/stabilized heterogeneous mixtures and have large acid neutralizing capacity, thus rendering true assessment of leaching potential impractical. This is particularly important for the assessment of long-term leaching potential of a solid waste. As a regulatory screening test, TCLP was not designed to account for several important parameters that significantly affect the kinetics of the reactions occurring at the solid-water interface including pH, reactant concentrations, reprecipitation reactions and secondary phase formations, physical characteristics of the solid wastes, residence time, and temperature. The need for reliable assessment and prediction of leaching behavior of waste materials has evoked a need to incorporate these factors in evaluating the leaching behavior of waste materials generated anthropogenically or naturally.